Safety device for power-hoists



A. LEVEDAHL. SAFETY DEVICE FOR POWER HOISTS.

APPLICATION FILED SEPT. 22, I9I9- 0 2. 9 IT H 0 3H T H Nw as w m a D1 A. L EVEDAHL.

SAFETY DEVICE FOR POWER HOISTS.

AFPLICATIQN FILE'D SEPT. 22, 1919; 1,3 0, 52, I Patented Nov. 30,1920.

3 SHEETS-SHEET 2- jzz/a'flbr I #2365 ZeuaW A. LEVEDAHL. SAFETY DEVICE FOR PowER HOISTS.

APPLICATION FILED SEPT. 22, I919.

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ILLINOIS, A CORPORATION OF DELAWARE.

SAFETY DEVICE FOR POWER-HOISTS.

Application filed September 22, 1919.

To all whom it may concern:

Be it known that I, AxEL LEVEDAHL, a citiaen of the United States, residing at Aurora, 111 the county of Kane and State of Illinois, have invented new and useful Improvements in Safety Devices for Power-Hoists, of which the following is a specification.

This invention relates to a safety device for power hoists and has for its object to automatically release the power connection between the motor and the drum and stop the rotation of the latter as soon as the cable loosens on the drum, thereby avoiding injury or damage to the cable and the other parts of the device whenever such a condition occurs in the operation of the hoist.

In power hoists, when one drum is used, one end of the cable is connected with the drum and the other or free end is provided with a lifting hook or other part for engaging a load to be handled, while when two drums are employed, both ends of the cable are secured to the drums, with the lifting hook engaged with the free loop in the cable. The cable wraps about the drum in a coil in the winding of the cable thereon, and in many instances a guard or casing surrounds the drums for housing and-protective purposes. IVhen the cable is being unwound by the motor, a certain weight must be on the descending end or loop of the cable to maintain sufficient tension thereon to hold the same about the drums, otherwise the cable would not unwind properly, but would recoil and loosen up partly on the drum and touch the guard or casing. The cable would stop playing out, and being fastened to the drum, it would forcibly expand under the guard or casing to such an extent as to break such part and injure the cable as well. If the drum continues to rotate in the unwinding direction, the disaster would become greater. If no guard or casing were used, the cable would still freely unwind.

from the drum or drums and disaster of another sort would follow, such as would happen in an elevator, should the car in its descent, become stuck in the shaft. In hoists, the loosening of the cable would occur, should its descending-end or loop, or the load attached thereto, come to rest on the floor or other object, or should the descending end be lifted by the hand of a workman for any purpose, while the drum or drums continue to rotate in unwinding direction.

Specification of Letters Patent.

Patented Nov. 30, 1920.

Serial No. 325,446.

This would release the required weight from the cable while being unwound, and cause the damage mentioned, if the drum or drums were not stopped at that time.

The safety device of my invention prevents and guards against the occurrence of such accidents, and in the accompanying drawings illustrating the same,

Figure 1 is a vertical sectional view through a portable power hoist equipped with a safety device of my invention,

Fig. 2 is a vertical sectional view taken on line 2 of Fig. 1. V

Fig. 3 is a side elevational view of the worm gear to which my invention is applied, in the particular type of hoist shown, the removable side plate of the gear being removed to show the arrangement of the pawls and other parts within the gear.

Figs. l and 5 are sectional views taken on lines 44 and 5-5 respectively, of Fig. 3; and

Fig. 6 is a perspective view of one of the pawls.

In the drawings, I have shown a safety device of my invention incorporated in a portable power hoist of the type forming the subject of the pending application of Reinhold A. Norling, Serial Number 316,79&, filed August 11, 1919, and as illustrated in Figs. 1 and 2 hereof, said hoist comprises in its general features, a hollow casing or guard 1, having a mid-frame 2, and drum covers 3, 3, secured thereto on opposite sides of the same, by bolts 4. Through the casing 1 extends a stationary shaft 5 with its ends supported in the end webs 6 of the drum covers, the central portion of said shaft extending through and supported by an internal web 7 of the mid-frame. Located in the casing 1, are two drums 8, 8, rotatably mounted on said shaft 5 and arranged with a drum on each side of the web 7. Each drum 8 is provided in its outer cylindrical surface with a continuous, spiral or helical groove 9, extending about the drum from its inner to its outer end and of a size to receive a hoisting rope or cable 10. The drums are alike in size and the grooves 9 therein are the same in pitch and extend in reverse directions, so that the single cable used has one portion wrapped in a single A layer on each drum. The ends of the cable are rigidly secured to the drums at their outer ends as at 11, 11 in Fig. 2, there being one end of the cable secured to one drum and the other end to the other drum. The free loop at the mid-portion of the cable is on the outside of the casing 1 and is trained about a grooved pulley or sheave, journaled in a frame carrying a .swiveled hoisting hook or its equivalent, for enabling the cable to be engaged with a load to be raised in the winding of the cable on the drums. Located in the casing 1, between the drums 8, 8, is a shaft 12 provided with a worm 13 in mesh with a worm gear 14 keyed or otherwise fixed to a shaft 15 below the shaft 12. Said shaft 12 is supported at its ends in the casing 1 by roller bearings 16, 16, and an end thrust bearing 17, as shown. Said shaft 15 is provided on each side of the worm gear 14 with a gear pinion 18, 18, rotatable therewith and constantly in mesh with a gear wheel 19 on the inner end of the associated drum 8. The gear pinions 18, 18 have the same diameter and so have the gear wheels 19, 19, so that the drums will rotate at the same rate of speed and wind the pertions of the cable thereon evenly and to the same extent. For rotating the drums, there.

is a motor 20 secured to the casing 1 on the outside thereof and in the particular device illustrated, said motor is of the air-actuated or pneumatic type, having cylinders andreciprocating pistons therein for turning a crank shaft 21 connected with the worm shaft 12. Said motor .20 is provided with a valve device for controlling the supply of motive fluid thereto and with starting, stopping and reversing mechanism, so that the drums 8, 8, may be rotated in one direction to wind the cable 10 thereon, and be rotated in the opposite direction to unwind the cable therefrom. Such mechanism is fully described in the pending application mentioned, and needs no further illustration or description herein, as I merely show enough of the hoist and motor structure to make clear the application of my invention thereto.

e As shown in Fig. 2, the guard or casingl surrounds and protects the drums, the cylindrical walls of the drum covers being closely adjacent the drums and providing between the parts an annular space 22 sufficient to receive a single layer of the cable when properly wound on the drums.

In the particular type of hoist shown, the safety device of my invention is appliedto the worm gear 14 in order to control both drums and is constructed as follows. As shown in Figs. 3 to 5, said worm. gear 14 comprises two main members, an inner member 23 connected with the shaft 15 to rotate therewith at all times, and an outer member 24 in meshwith the worm 13 on the shaft 12, said members being rotatably mounted upon each other and releasably connected together by one or more spring pressed pawls 25, permitting one member to rotate relative to the other when the occasion demands. The inner member 23, as shown in the drawings, is in the form of a hub or ring having a key slot 26 for permitting connection with said shaft 15. The outer member 24 is in the form of a gear wheel having teeth for meshing with the worm 13. Said member 24 is larger in diameter than the inner member 23 and is provided at each side thereof with an inwardly extending, annular flange 27, 28, which seat in annular grooves or recesses 29, 30, provided in the hub 23. By this construction, the inner and outer members of the Worm gear are connected together laterally, but are permitted to rotate relatively to each other. The flanges 27, 28, also space the members apart radially, to permit the pawls to be locatedbetween the same. Each pawl 25, when more than one is used, has one end rockably mounted in the outer member 24 and its other or free end bearing against the adjacent cylindric surface of the inner member or hub 23. Such surface of the hub 23 is provided with V-shaped notches 31, one for each pawl. The free or swinging ends of the pawls are normally held in the notches by springs 32, one for each pawl and attached in a suitable manner to the gear member 24, as for instance, by being looped at 33 about a pin 34 fixed in the member 24. When so made, one end of the spring bears against the gear member 24, and the other end against the pawl, as shown. To permit the pawl to engage the 100 hub 23 and to move uninterrupted into and out of engagement with such part, the gear member 24 is provided with a circular shaped recess or cavity 35 for each pawl, and with a communicating recess or groove 105 36 for the spring. One of the flanges, namely, the one 28, at one side of the gear member 24 is in the form of an annular plate removably connected with the gear member by fastening screws or like parts 110 37, so that the inner and outer members of the worm gear may be separated for applying the springs and pawls thereto or removing such parts therefrom when the plate 28 is taken off.

When the worm gear 14, so made, is placed in the train of gears in the hoist, as shown in Figs. 1 and 2, to provide a power transmitting connection between the motor 20 anddrums 8, there is then a device 120 between the drums and the motor, acting automatically to release the power connections between such parts. whenever the cable loosens fronnthe drums and touches the easing or guard 1. As shown in Fig. 3, when 125 the pawls 25 engage in the notches 31, the. worm gear 14 will be rotated with the shaft 2 15 in either direction,. and thus the cable may be wound on or unwound from the drums in the operation of the motor. 130

Should the cable, while being unwound, loosen on the drums, one or more of the coils of the cable would expand and as soon as contact with the casing 1 was made, the expanding cable would stop playing out and act to stop the rotation of the drums. Under such a condition, the shaft 15 and hub 23 would stop, and the pawls 25 WOUlCl be released from the notches in the hub 23. This would release the power connection between the motor and the drums. The motor, however, would continue to revolve the shaft 12, worm l3, and outer member of the worm gear 14, without rotating the drums. Thus, the cable would not be expanded any further and the parts prevented from injury or damage, even though the motor continues to rotate in an unwinding direction. Manifestly, with a safety device of my invention in use in a hoist, no damage would be produced should the required weight on the descending end of the cable be released in any manner whatever, during the time that the drums are being rotated to unwind the cable.

It is to be, of course, understood that the safety device described, could be placed at any other place in the power transmitting mechanism provided between the motor and the drums, as for instance in the worm shaft 12, or in each of the gear wheels 18 01 19. But by placing the safety device n the worm gear 14:, only one deviceis required to control both drums.

lVhile I have shown and described one form of safety device embodying the features of my invention, it is to be understood that the details of construction and arrange- .ment of parts shown and described could be variously changed and modified without departing from the spirit and scope of my invention.

I claim as my invention:

1. In a hoisting device, the combination with two drums geared together to rotate in unison .and in the same direction, and a single cable connected with and adapted to have a portion wound about each of said drums, of a motor for rotating said drums, and means for automatically releasing the power connection between the motor and both drums when the rotation of either drum is stopped, as by the loosening of the cable thereon.

2. In a hoisting machine, the combination with two drums and a single cable connected with and adapted to have a portion wound about each of said drums, of a motor for rotating said drums, power transmitting mechanism connecting the motor with both drums and gearing the drums together to be rotated in unison and in the same direction, and means in said mechanism for automatically releasing the power connection between the motor and both drums when the rotation of either drum is stopped, as by the loosening of the cable thereon.

8. In a hoisting device, the combination "with two drums and asingle cable connectsame direction, and means releasably connecting said rotative member with said motor for automatically disconnecting the motor from both drums when the rotation of either drum is stopped, as by the loosening of the cable thereon.

4. In a hoisting device, the combination with a drum and a cable therefor, of a motor for rotating said drum, a train of gears providing a power transmitting connection between the motor and said drum, one of the gear wheels comprising two members rotatably mounted on each other and with one having driving connection with said motor and the other with said drum, and means interposed between said members for releasably connecting the same together for automatically disconnecting the motor from said drum when the rotation of the latter is stopped, as by the loosening of the cable thereon.

5. In a hoisting device, the combination with a drum and a cable therefor, of a motor for rotating said drum, a train of gears providing a power transmitting connection between the motor and said drum, one of said gear wheels comprising two annular members rotatably mounted on each other, one having driving connection with said motor and the other with said drum, and a pawl carried by one of said members and engaging a notch in the other of said members for automatically releasing the driving connection between said members when the rotation of the drum is stopped, as by the loosening of the cable there-on.

6. In a hoisting device, the combination with two drums geared together to rotate in unison and in the same direction, and a single cable connected with and adapted to have a portion wound about each of said drums, and a guard or casing surrounding each drum, of a motor for rotating said drums, and means for automatically releasing the power connection between the motor and both drums when the rotation of either drum is stopped, as by the cable loosening on the drum and coming into contact with the guard or casing.

7. In a hoisting device, the combination with two drums and a single cable connected with and adapted to have a. portion wound about each of said drums, of a motor for rotating said drums, a train of gears providing a power transmitting connection between the motor and both drums for rotating the latter in unison and in the same direction, one of the gear wheels being common to both drums and having a driving connection with each, said gear wheel being provided with means for automatically releasing the power connection between the motor and both drums when the rotation of either drum is stopped, as by the loosening of the cable thereon.

8. In a hoisting device, the combination with two drums spaced apart endwise, and a cable connected with and adapted to have a portion wound about each drum, of a motor, a shaft rotated by said motor and extending between said drums, a worm on said shaft, a worn wheel between said drums, and meshing with said worm, said Worm wheel comprising two annular members rotatably mounted on each other with the outer one meshing with said worm, and the inner one geared to both drums to rotate the same in unison and in the same direction, and a pawl carried by the outer member and engaging a notch in the inner member for automatically releasing both drums from the motor when the rotation of either drum is stopped, as by the loosening AXEL LEVEDAHL. 

